Generally, projectors are devices for projecting an image on a picture screen. Projectors are classified into two types: color cathode-ray tube projectors displaying an image by radiating light emitted from red R, green G, and blue B cathode-ray tubes through an optical system; and projectors using a reflection-type ferroelectric liquid crystal display shutter employing random access memory(RAM) devices.
Referring to FIG. 9 illustrating a projector employing a ferroelectric liquid crystal display shutter, the projector comprises red R, green G, and blue B light sources 2, a first condensing lens 4 for converting light radiated from the light sources 2 into beams, a diffuser 5 for diffusing the beams, a polarizing beam splitter(PBS) 6 for selecting and polarizing a predetermined directional light in the incident light passing through the first condensing lens 4 and the diffuser 5, a ferroelectric liquid crystal(FLC) shutter 8 on/off operated according to the polarizing operation of the PBS 6 and comprising a reflecting layer attached a side opposite that facing the PBS 6(backside) and a very large scale integrated (VLSI) circuit having RAM devices attached on each pixel, and an optical system 10 for magnifying and projecting at a predetermined ratio the light reflected from the ferroelectric liquid crystal shutter 8 on a picture screen.
A variety of lamps able to emit white light, e.g., light emitting diodes or metal halide lamps, may be used for the light sources 2.
The ferroelectric liquid crystal shutter 8 includes FLC pixels each having a RAM device attached thereon, and an aluminum (Al) reflecting layer attached on the backside of the shutter 8.
The ferroelectric liquid crystal shutter 8 is on/off operated according to the polarizing operation of the PBS 6 by adjusting an optical axis exterior electric field of the FLC.
The optical system 10 magnifies the image obtained from the ferroelectric liquid crystal shutter 8 through a lens system, then projects the magnified image on a picture screen, thereby obtaining an image of a reflection-type active matrix ferroelectric liquid crystal projection display.
The projector using the reflection-type ferroelectric liquid crystal shutter 8 employing RAM devices may display natural colors such as red R, green G, and blue B by utilizing a time-sharing operation. This type of projector may solve the problem of the response speed when obtaining a dynamic picture image since the projector has the advantages both of the active matrix actively operating each pixel of the ferroelectric liquid crystal by employing RAM devices and of the ferroelectric liquid crystal display having a rapid response speed. As a result, three reflection-type shutters for red R, green G, and blue B are not required but only one shutter is enough to realize images with the red R, green G, and blue B colors. Accordingly, the structure of the projector is simplified and manufacturing costs are reduced.
However, drawbacks remain in the above described conventional projector. Namely, because a reflection-type image is projected, a user viewing range is limited, the image appearing unclear and deformed at some angles, and brightness is reduced.
Further, the conventional projector passively emits light. That is, since the image is obtained by reflection or transmission and not by active emission of pixels, user viewing range, picture quality, and brightness are negatively affected. As a result, the conventional projector cannot be used for small-sized projectors but only for large-sized projectors having a screen size of 40 inches or more.